The present invention is generally related to sensor methods and devices. The present invention is also related to temperature sensing methods and devices. The present invention is additionally related to thermostat control devices. The present invention is further related to magnetic sensor methods and devices. The present invention also relates to switching methods and devices, particularly thermostat control switching devices thereof.
Thermostat control devices are often utilized in heating and cooling systems in buildings, homes, and industrial applications such as power plants. Thermostat control devices are required, for example, to control power to a furnace or air conditioner blower motor, which is typically an AC induction motor. In heating, ventilation and air-conditioning (HVAC) systems, such as home air conditioning systems, it is often desirable to change the fan speed or blower speed to control the amount of airflow through the system""s evaporator coil. In addition, in the initial operation in an air conditioning mode, the blower operates at high speed to pump conditioned air, especially to higher floors. Then, when the comfort space or living space has cooled down, the fan speed can be reduced to avoid blowing cold air directly on human occupants.
A number of electrical switching applications require mechanical switches that are both efficient and reliable. These requirements arise commonly in electromechanical thermostats utilized in the thermostat control of heating and cooling systems in homes and buildings indicated above. In such configurations, coils of standard bi-metallic strips can form the switch actuation elements. For many years this thermostatic switching function has been performed by mercury bulb switch elements. Thermostat control devices in use today generally operate utilizing a bi-metallic strip that changes angularity with temperature, tilting a mercury switch so that the mercury can move to make or break contacts, using the self leveling nature of the mercury itself.
One of the problems associated with mercury-based switching devices is the mercury itself, which presents a number of dangerous environmental hazards, as well as danger to humans and animals. Mercury-based thermostat switching devices have been under heavy scrutiny from environmentalists to eliminate the use of mercury. Thus, it is only a matter of time before mercury-based thermostat switching devices fall entirely out of favor. An alternative solution must be found, particularly because it is anticipated that the use of mercury will soon be banned entirely.
Other solutions have included finding a replacement for mercury or employing metallic spheres rolling in a glass tube to come into contact with switching electrodes, imitating a mercury switch, although not very successfully. Other attempts have involved replacing the mercury switch with a reed switch. This particular approach has resulted in a number of accuracy problems. Other solutions have included the use of snap-action devices.
Snap-action switches have been utilized as control devices. The term xe2x80x9csnap-action switchxe2x80x9d generally refers to a low actuation force switch, which can utilize an internal mechanical apparatus to rapidly shift or snap the movable contact from one position to another to make or break electrical conduction between the movable contact and a fixed contact in response to moving an operating element of the switch, such as a plunger, a lever, a spring, or the like from a first to a second position. Typically, these switches require only a few millimeters of movement by the operating element to change the conduction state of the switch. Such switches generally operate at a current level of several amperes using the standard 24 VAC power which thermostats control.
When actuated by a low and slow actuation force, however, such as is provided by a thermostat""s coiled bi-metallic strip, snap-action switches can occasionally hang in a state between the two conducting states, or can switch so slowly between the two conducting states that unacceptable arcing can occur when entering the non-conducting state. Either condition can give rise to unacceptable reliability and predictability of operation. Furthermore, these switches frequently have unacceptably large differentials. Current switches also contain a heating circuit that actually changes the bi-metallic strip by adding heat to it. The amount of heat applied is generally adjustable by use of an adjustable wire-wound resistor. In this sense, such devices do not truly respond to a change based on the room temperature. Additionally, mercury-based devices exhibit a weight problem associated with the use of mercury, which can affect the sensitivity of the device. The present inventors have thus recognized that a need exists for a temperature-sensitive switching device that responds directly to room air temperature, and one that also avoids the weight and environmental issues associated with mercury.
Based on the foregoing, the present inventors have concluded that a solution to such problems can be achieved through the use of Hall-effect sensors, which are sensor devices that operate according to the Hall effect. The Hall effect is well known in the magnetic sensing arts. Hall-effect sensors are typically based on the utilization of a Hall generator, which generally comprises a magnetic field-dependent semiconductor whose function rests on the effect discovered by Edwin Hall. This effect, known as the xe2x80x9cHall effectxe2x80x9d is caused by the Lorentz force, which acts on moving charge carriers in a magnetic field. The Hall effect occurs when the charge carriers moving through a material experience a deflection because of an applied magnetic field. This deflection results in a measurable potential difference across the side of the material, which is transverse to the magnetic field and the current direction.
One of the first practical applications of the Hall effect was as a microwave power sensor in the 1950s. With the later development of the semiconductor industry and its increased ability for mass production, it became feasible to use Hall effect components in high volume products. Honeywell International Inc. (xe2x80x9cHoneywellxe2x80x9d), a company headquartered in Morristown, N.J., for example, has been a leader in Hall effect applications. In 1968, Honeywell""s MICROSWITCH division produced a solid-state keyboard using the Hall effect. The Hall-effect sensing element and its associated electronic circuit are often combined in a single integrated circuit to form a Hall-effect sensor thereof. Note that the term xe2x80x9cHall-effect sensorxe2x80x9d and xe2x80x9cHall sensorxe2x80x9d are generally utilized interchangeably to refer to the same type of device. Thus, Hall sensors are well known in the magnetic sensing arts.
In the simplest form of a Hall sensor, a Hall element can be constructed from a thin sheet of conductive material with output connections perpendicular to the direction of electrical current flow. When subjected to a magnetic field, the Hall-effect element responds with an output voltage that is proportional to the magnetic field strength. The combination of a Hall-effect element in association with its associated signal conditioning and amplifying electronics is sometimes called a Hall-effect transducer.
A number of types of Hall-effect sensors are currently utilized in commercial, consumer and industrial applications. Honeywell, for example, produces a family of solid-state position sensors that include digital and analog Hall-effect position sensors, magnetoresistive digital sensors, Hall-effect vane sensors, gear tooth sensors, Hall-effect basic switch, and various types of magnets thereof. Such solid state position sensors are reliable, high speed, long life, sensors that are directly compatible with other electronic circuits. These sensors respond to the presence or the interruption of a magnetic field by producing either a digital or an analog output proportional to the magnetic field strength. Digital and analog xe2x80x9csensor-onlyxe2x80x9d devices are operated by the magnetic field from a permanent magnet or electromagnet.
The actuation mode associated with such sensors depends generally on the type of magnets used. Either a vane passing through a gap or a magnet mounted on a plastic plunger, for example, can operate integral magnet position sensors. Such position sensors can be implemented in accordance with applications that require accurate, reliable outputs. They are found in brushless DC motors, utility meters, welding equipment, vending machines, home appliances, computers, and so on. Typical applications include ignition timing, power, sensing, valve positioning, robotics control, current sensing, linear or rotary motion detection, length measurement, flow sensing, RPM sensing, and security systems.
The present invention disclosed herein thus offers a unique solution to the problems associated with conventional thermostat control devices, particularly those devices which are mercury-based. The present invention essentially eliminates the need for a mercury switch by replacing the switching and temperature components thereof with an electro-mechanical solution.
The following summary of the invention is provided to facilitate an understanding of some of the innovative features unique to the present invention and is not intended to be a full description. A full appreciation of the various aspects of the invention can be gained by taking the entire specification, claims, drawings, and abstract as a whole.
It is, therefore, one aspect of the present invention to provide improved sensor methods and devices.
It is, therefore, another aspect of the present invention to provide a temperature sensing method and apparatus.
It is yet another aspect of the present invention to provide a thermostat control device, including a method and apparatus thereof.
It is yet another aspect of the present invention to provide a magnetic sensor method and apparatus.
The above and other aspects of the invention can be achieved as is now described. Methods and devices for magnetically detecting a temperature change for thermostat control thereof are disclosed herein. A thermostat control device can be configured to include at least one bi-metallic strip that experiences a change in angular position in response to a temperature change. The thermostat control device is generally associated with a Hall sensor, which includes one or more magnets that experience a movement relative to the Hall sensor and in response to the change in the angular position of the bi-metallic strip. The temperature change can then be automatically and/or electrically detected in response to the movement of the magnets. Thus, the temperature change is utilized for thermostat control thereof.
The Hall sensor can include one or more Hall transistors. Such Hall transistors are associated with the magnet(s) described herein. A change in state of the Hall transistor can thus occur in response to the change in the angular position of the bi-metallic strip. Such a change in state generally comprises a change from a low state to a high state. The thermostat control device is generally associated with a furnace having a power load thereof. Such a thermostat control device can also be associated with microprocessor control circuitry for furnace control thereof.
The output of the Hall sensor can be utilized to accomplish a number of thermostat control operations. For example, the output of the Hall sensor can be coupled to a switching device for shifting the power load of the furnace. For example, coupling of the Hall sensor to the switching device can be accomplished utilizing a relay (e.g., a low current relay) or a coil (e.g., a magnetic reed switch). Additionally, the Hall sensor can be located perpendicular to an opposing magnetic field. The magnets of the Hall sensor can be arranged to include one or more magnets located proximate to one another such that a sudden linear change from a positive gauss to a negative gauss is generally established. The magnets are preferably located on a radial surface of the bi-metallic strip, which can be configured as a coiled bi-metallic strip located within the thermostat control device itself.
The novel features of the present invention will become apparent to those of skill in the art upon examination of the following detailed description of the invention or can be learned by practice of the present invention. It should be understood, however, that the detailed description of the invention and the specific examples presented, while indicating certain embodiments of the present invention, are provided for illustration purposes only because various changes and modifications within the spirit and scope of the invention will become apparent to those of skill in the art from the detailed description of the invention and claims that follow.